Heat pump and hvac system architecture for electric vehicles

ABSTRACT

An HVAC system of an electric vehicle includes a housing having an inlet for receiving a flow of air therethrough and an air outlet in fluid communication with a passenger compartment of the vehicle. The HVAC system further includes a first heat exchanger disposed in the housing and a second heat exchanger disposed in the housing downstream from the first heat exchanger with respect of a direction of the flow of air through the housing. A primary circuit containing a flow of refrigerant therethrough is in fluid communication with the first heat exchanger. A secondary circuit is in one of fluid communication with and heat exchange communication with the primary circuit and in fluid communication with the second heat exchanger.

FIELD OF THE INVENTION

The invention relates to a heating, ventilating, and air conditioning (HVAC) system of a vehicle, and more particularly to an HVAC system of an electric vehicle having a heat exchanger for combined refrigeration plant and heat pump operation of the HVAC system for heating, cooling, and dehumidifying air to a passenger compartment and an auxiliary heater for use when dehumidifying the air to the passenger compartment.

BACKGROUND OF THE INVENTION

As commonly known, a vehicle typically includes a climate control system which maintains a temperature within a passenger compartment of the vehicle at a comfortable level by providing heating, cooling, and ventilation. Comfort is maintained in the passenger compartment by an integrated mechanism referred to in the art as a heating, ventilating and air conditioning (HVAC) system. The HVAC system conditions air flowing therethrough and distributes the conditioned air throughout the passenger compartment.

Typically, in operation, a compressor of an HVAC system provides a flow of fluid having a desired temperature to an evaporator disposed in the HVAC system to condition the air. The compressor is generally driven by a fuel-powered engine of the vehicle, such as an internal combustion engine. The traditional HVAC systems are known to provide heating during a heating mode, cooling during a cooling mode, and dehumidification during a demist mode to the passenger compartment. During the demist mode, when ambient temperatures are above 20° C., the air flowing through the HVAC to the passenger compartment is first cooled and sufficiently dehumidified. The cooled air is then reheated to provide desired comfort for the passenger compartment. The traditional HVAC systems use waste heat from the internal combustion engine to provide heat during the heating mode and heat during the demist mode to reheat the cooled air.

However, vehicles having improved fuel economy over the fuel-powered engine and other vehicles are quickly becoming more popular as a cost of traditional fuel increases. An example of vehicles having improved fuel economy are electric vehicles. Electric vehicles include an electric motor powered by an energy source such as a battery, for example. However, electric vehicles do not provide the requisite amount of waste heat to desirably heat the air flowing through the HVAC system to the passenger compartment during the heating mode or the demist mode.

Accordingly, HVAC systems for electric vehicles are known to include a combined refrigeration plant and heat pump operation for heating, cooling, and dehumidifying the passenger compartment of the vehicle. However, these systems are unable to provide reheating during the demist mode due to the absence of the waste heat from the fuel-powered engine. To overcome this deficiency, additional electrical elements such as a positive temperature coefficient PTC heaters are used for reheating. However, the electrical elements use energy drawn from the electrical system, thus reducing the overall efficiency of the electric vehicle.

Therefore, other systems of reheating air during a demist mode can be employed. For example, in U.S. Patent No. 2007/0283703, an air conditioning unit for combined refrigeration plant and heat pump operation is disclosed. The air conditioning unit includes a primary circuit and a secondary passage. The primary circuit includes a gas cooler and an evaporator. The secondary passage includes a gas cooler. The secondary passage is used during the heat pump operation to heat air that has been dehumidified. Although adequate for providing combined refrigeration and heat pump operation for heating, cooling, and dehumidification, these systems are inefficient.

Additionally, HVAC systems commonly employ housings with an air flow conduit to convey air from an air source to the passenger compartment. The air flow conduit of the HVAC systems can be divided into two or more passages. At least one of the passages includes a heater core for heating the air. The housing may include blend doors to direct a flow of the air through one or more passages to either heat the air, cool the air, or dehumidify the air. Although adequate for heating, cooling, and dehumidifying, the HVAC system including housings with blend doors may occupy a greater volume of vehicle space, increase noise and vibrations, and include added complexity. An example of the HVAC system including a housing with blend doors is described in U.S. Pat. Appl. Pub. No. 2013/0105126.

Furthermore, electrical vehicles have an additional constraint in that the battery of the electric vehicle must be cooled to maintain optimal efficiency of the electric vehicle. In an electric vehicle, propulsion is provided by the battery. Energy is stored in the battery to drive the electric battery. When energy is stored or discharged from the battery assembly, heat is generated within the battery. Heat minimizes the performance efficiency of the battery which, consequently minimizes the performance efficiency of the electric vehicle.

While the known HVAC systems perform adequately, it is desirable to provide an HVAC system for an electric vehicle and a method of operating an HVAC system for an electric vehicle, wherein an effectiveness and efficiency of the HVAC system and the electric vehicle is maximized while maintaining cost, weight, and package space requirements.

SUMMARY OF THE INVENTION

In accordance and attuned with the present invention, an HVAC system for an electric vehicle and method of operating the HVAC system for an electric vehicle, wherein an effectiveness and efficiency of the HVAC system and electric vehicle is maximized while maintaining cost, weight, and package space requirements has surprisingly been discovered.

According to an embodiment of the disclosure an HVAC system of an electric vehicle is disclosed. The HVAC system includes a housing having an inlet for receiving a flow of air therethrough and an air outlet in fluid communication with a passenger compartment of the vehicle. A first heat exchanger is disposed in the housing and configured to receive the flow of air therethrough. A second heat exchanger is disposed in the housing downstream from the first heat exchanger with respect of a direction of the flow of air through the housing. The second heat exchanger is configured to receive the flow of air. A primary circuit contains a flow of refrigerant therethrough and is in fluid communication with the first heat exchanger. The primary circuit includes a compressor, a third heat exchanger, at least one expansion valve, and a plurality of valves. Each of the valves cooperating with each other to selectively convey the flow of refrigerant through the first heat exchanger in a first direction and a second direction. A secondary circuit is in one of fluid communication with and heat exchange communication with a portion of the primary circuit intermediate the third heat exchanger and the at least one expansion valve. The secondary circuit is in fluid communication with the second heat exchanger.

According to another embodiment of the disclosure a method for operating an HVAC system of an electric vehicle id disclosed. The method includes the steps of providing a housing having an inlet for receiving a flow of air therethrough and an outlet in fluid communication with a passenger compartment of the vehicle. The method includes the step of disposing a first heat exchanger in the housing and a second heat exchanger in the housing downstream from the first heat exchanger with respect of a direction of the flow of air. Additionally, the method includes the step of providing a primary circuit containing a flow of refrigerant therethrough and configured to operate in at least a cooling mode, a demist mode, and a heating mode. The primary circuit has a compressor, a third heat exchanger, and at least one expansion valve each in fluid communication with the first heat exchanger. The method further includes the steps of directing the flow of refrigerant through the first heat exchanger in a first direction during the cooling mode and the demist mode and in a second direction during the heating mode and providing a secondary circuit in fluid communication with the second heat exchanger and in one of fluid communication with and heat exchange communication with a portion of the primary circuit intermediate the third heat exchanger and the at least one expansion valve.

According to a further embodiment of the disclosure a method for operating an HVAC system of an electric vehicle id disclosed. The method includes the steps of providing a housing having an inlet for receiving a flow of air therethrough and an outlet in fluid communication with a passenger compartment of the vehicle. The method includes the step of disposing a first heat exchanger in the housing and a second heat exchanger in the housing downstream from the first heat exchanger with respect of a direction of the flow of air. Additionally, the method includes the step of providing a primary circuit containing a flow of refrigerant therethrough and configured to operate in at least a cooling mode, a demist mode, and a heating mode. The primary circuit has a compressor, a third heat exchanger, and at least one expansion valve each in fluid communication with the first heat exchanger. The method includes the steps of directing the flow of refrigerant through the first heat exchanger in a first direction during the cooling mode and the demist mode and in a second direction during the heating mode and providing a secondary circuit in fluid communication with the second heat exchanger and in one of fluid communication with and heat exchange communication with a portion of the primary circuit intermediate the third heat exchanger and the at least one expansion valve. The method further includes the step of directing one of the flow of refrigerant and a flow of coolant through the second heat exchanger during the demist mode.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as other objects and advantages of the invention, will become readily apparent to those skilled in the art from reading the following detailed description of a preferred embodiment of the invention when considered in the light of the accompanying drawing which:

FIG. 1 is a schematic flow diagram of an HVAC system according to an embodiment of the present disclosure, the HVAC system configured to operate in a cooling mode, dehumidifying mode, and a heating mode;

FIG. 2 is a schematic flow diagram of the HVAC system of FIG. 1, illustrating the HVAC system operating in the cooling mode thereof;

FIG. 3 is a schematic flow diagram of the HVAC system of FIG. 1, illustrating the HVAC system operating in the demist mode thereof;

FIG. 4 is a schematic flow diagram of the HVAC system of FIG. 1, illustrating the HVAC system operating in the heating mode thereof;

FIG. 5 is a schematic flow diagram of an HVAC system according to another embodiment of the present disclosure, the HVAC system configured to operate in a cooling mode, dehumidifying mode, and a heating mode;

FIG. 6 is a schematic flow diagram of the HVAC system of FIG. 5, illustrating the HVAC system operating in the cooling mode thereof;

FIG. 7 is a schematic flow diagram of the HVAC system of FIG. 5, illustrating the HVAC system operating in the demist mode thereof; and

FIG. 8 is a schematic flow diagram of the HVAC system of FIG. 5, illustrating the HVAC system operating in the heating mode thereof.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description and appended drawings describe and illustrate various embodiments of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner. In respect of the methods disclosed, the steps presented are exemplary in nature, and thus, the order of the steps is not necessary or critical. Except where otherwise expressly indicated, all numerical quantities in this description are to be understood as modified by the word “about” in describing the broadest scope of the technology.

FIG. 1 illustrates a heating, ventilating, and air conditioning (HVAC) system 10 according to an embodiment of the disclosure. The HVAC system 10 typically provides heating, ventilation, and air conditioning for a passenger compartment of an electric vehicle (not shown). The electric vehicle includes a battery 11 for providing power to an electric motor (not shown) of the electric vehicle.

The HVAC system 10 includes a hollow casing or housing 12 for conveying air therethrough. The housing 12 includes an air inlet 18 and an air outlet 19. The air inlet 18 is in fluid communication with a supply of air (not shown). For example, the supply of air can be provided from outside of the vehicle, recirculated from the passenger compartment of the vehicle, or a mixture of the two. The air outlet 19 is in fluid communication with the passenger compartment. The housing 12 is adapted to receive a blower (not shown) disposed adjacent the air inlet 18 to convey the air through the housing 12. It is understood other components for conditioning the air can also be disposed upstream or downstream of the air inlet 18 with respect of a direction of the flow of air through the housing 12, as desired. For example, a filter can be disposed upstream or downstream of the air inlet 18 with respect of a direction of the flow of air through the housing 12.

The housing 12 is configured to receive a first heat exchanger 14 and a second heat exchanger 16. Each of the first heat exchanger 14 and the second heat exchange 16 conditions the air flowing through the housing 12. The second heat exchanger 16 is disposed in the housing 12 downstream from the first heat exchanger 14 with respect of a direction of the flow of air through the housing 12. The first heat exchanger 14 can be any conventional type of heat exchanger configured to provide heat transfer between the the air flowing through the housing 12 and a fluid. The first heat exchanger 14 is further configured to operate as both an evaporator to cool the air flowing through the housing 12 and a heater core, or a secondary condenser, to heat the air flowing through the housing 12. The second heat exchanger 16 is a heat exchanger configured to provide heat transfer between the air flowing through the housing 12 and a fluid.

In the embodiment illustrated in FIG. 1, for example, the second heat exchanger 16 is separate from the first heat exchanger 14. However, the second heat exchanger 16 can be integrally formed with the first heat exchanger 14, coupled to the first heat exchanger 14, or abutting the first heat exchanger 14. Furthermore, in certain embodiments, the second heat exchanger 16 has dimensions smaller than the first heat exchanger 14. For example, the second heat exchanger 16 can have a thickness equal to 40 percent of the thickness of the first heat exchanger 14. However, it is understood the second heat exchanger 16 can have any thickness or other dimensions as desired dependent upon vehicle performance and package requirements, as desired.

The HVAC system 10 further includes a primary circuit 20 in fluid communication with the first heat exchanger 14 and a secondary circuit 30 in fluid communication with the second heat exchanger 16. The primary circuit 20 is illustrated in FIG. 1 with solid lines and the secondary circuit 30 is illustrated with dash lines. The primary circuit 20 is configured as a reversible heat pump circuit. The primary circuit 20 conveys a refrigerant through the first heat exchanger 14 to either cool the air flowing through the first heat exchanger 14 or heat the air flowing through the first heat exchanger 14. The refrigerant can be any refrigerant such as R134a, HO-1234yf, AC-5, AC-6, or CO₂, for example. The primary circuit 20 further includes a compressor 22, a third heat exchanger 24, a fourth heat exchanger 26, a first expansion valve 32, and a second expansion valve 33. It is understood the primary circuit 20 includes one or more conduits providing fluid communication between the various components (the first heat exchanger 14, the compressor 22, the third heat exchanger 24, the fourth heat exchanger 26, the first expansion valve 32, the second expansion valve 34) thereof.

The compressor 22 is in fluid communication with and disposed intermediate the first heat exchanger 14 and the third heat exchanger 24. The third heat exchanger 24 is in fluid communication with and disposed intermediate the compressor 22 and the fourth heat exchanger 26. The third heat exchanger 24 receives a flow of air from a supply of air. For example, the supply of air can be provided from outside of the vehicle. In certain embodiments, a fan 28 is disposed adjacent the third heat exchanger 24 to convey the air through the third heat exchanger 24. The third heat exchanger 24 can be any conventional type of heat exchanger configured to provide heat transfer between the air therethrough and the refrigerant flowing through the primary circuit 20.

The fourth heat exchanger 26 is disposed adjacent the third heat exchanger 24 intermediate the third heat exchanger 24 and the first heat exchanger 14. The fourth heat exchanger 26 is configured to provide heat transfer between the refrigerant flowing through the primary circuit 20 and a fluid. Each of the first expansion valve 32 and the second expansion valve 33 is disposed intermediate the fourth heat exchanger 26 and the first heat exchanger 14.

The primary circuit 20 is configured to convey the refrigerant through the first heat exchanger 14 in both a first direction and a second direction. The primary circuit 20 includes a main pathway 34 for conveying the refrigerant through the primary circuit 20, and consequently through the first heat exchanger 14, in the first direction. The primary circuit 20 includes the first heat exchanger 14, the compressor 22, the third heat exchanger 24, the fourth heat exchanger 26, and the first expansion valve 32.

A first valve 42 is disposed in the main pathway 34 intermediate the first heat exchanger 14 and the compressor 22. The flow of refrigerant between the first heat exchanger 14 and the compressor 22 is controlled by the first valve 42. A second valve 44 is disposed in the main pathway 34 intermediate the compressor 22 and the third heat exchanger 24. The flow of refrigerant between the compressor 22 and the third heat exchanger 24 is controlled by the second valve 44. A third valve 46 is disposed in the main pathway 34 intermediate the fourth heat exchanger 26 and the first expansion valve 34. The flow of refrigerant between the fourth heat exchanger 26 and the first expansion valve 34 is controlled by the third valve 46. It is understood that more or fewer valves may be used as desired to control the flow of refrigerant through the main pathway 34 of the primary circuit 20.

The primary circuit 20 further includes a first bypass 36, a second bypass 38, and a third bypass 40. The bypasses 36, 38, 40 are configured for conveying the flow of refrigerant through the primary circuit 20, and consequently through the first heat exchanger 14, in the second direction. The first bypass 36 extends and conveys the refrigerant between a node A of the main pathway 34 of the primary circuit 20 intermediate the compressor 22 and the second valve 44 to a node B of the main pathway 34 of the primary circuit 20 intermediate the first heat exchanger 14 and the first valve 42. The second bypass 38 extends and conveys the refrigerant between a node C of the main pathway 34 of the primary circuit 20 intermediate the second valve 44 and the third heat exchanger 24 to a node D of the main pathway 34 of the primary circuit 20 intermediate the first valve 42 and the compressor 22. The third bypass 40 extends and conveys the refrigerant between a node E of the main pathway 34 of the primary circuit 20 intermediate the third valve 46 and the fourth heat exchanger 26 to a node F of the main pathway 34 of the primary circuit 20 intermediate the first expansion valve 32 and the first heat exchanger 14. It is understood that more or fewer bypasses can be used as desired to convey the refrigerant through the primary circuit 20.

The first bypass 36 includes a fourth valve 48 disposed therein. The flow of refrigerant through the first bypass 36 is controlled by the fourth valve 48. A fifth valve 50 is disposed in the second bypass 38 to control the flow of refrigerant through the second bypass 38. A sixth valve 52 is disposed in the third bypass 40 to control the flow of refrigerant through the third bypass 40. It is understood that more or fewer valves can be disposed in each of the bypasses 36, 38, 40 of the primary circuit 20, as desired.

The third bypass 40 further includes the second expansion valve 33 intermediate the sixth valve 52 and the first heat exchanger 14. The first expansion valve 32 is configured for receiving the flow of refrigerant conveyed through the primary circuit 20 in the first direction. The second expansion valve 33 is configured to receive the flow of refrigerant conveyed through the primary circuit 20 in the second direction.

The secondary circuit 30 conveys a coolant therethrough. The coolant can be any coolant such as a glycol coolant, for example. Although, other coolants can be used as desired such as water or a refrigerant, for example. The secondary circuit 30 is in fluid communication with the second heat exchanger 16 and the fourth heat exchanger 26. It is understood the secondary circuit 30 includes one or more conduits providing fluid communication between the various components (the second heat exchanger 16 and the fourth heat exchanger 26) thereof.

The secondary circuit 30 includes a main pathway 54 and a first bypass 56. A flow control device 58, such as a pump for example, is disposed in the secondary circuit 30 for causing the coolant to circulate therethrough. The flow control device 58 is disposed in the main pathway 54 of the secondary circuit 30 intermediate the second heat exchanger 16 and the fourth heat exchanger 26. However, the flow control device 58 can be disposed in the secondary circuit 30 at any position, as desired. A first valve 60 is disposed in the main pathway 54 of the secondary circuit 30 to control the flow of refrigerant through the main pathway 54 of the secondary circuit 30. It is understood that more or fewer valves can be disposed in the main pathway 54, as desired.

The first bypass 56 of the secondary circuit 30 is in heat exchange communication with the battery 11 of the electric vehicle. The first bypass 56 extends and conveys the flow of coolant between a node G of the main pathway 54 of the secondary circuit 30 intermediate the flow control device 58 and the fourth heat exchanger 26 and a node H of the main pathway 54 of the secondary circuit 30 intermediate the second heat exchanger 16 and the fourth heat exchanger 26. The first bypass 56 of the secondary circuit 30 includes a second valve 64 to control a flow of coolant through the first bypass 56 of the secondary circuit 30. It is understood that more or fewer valves can be disposed in the first bypass 56, as desired.

In certain embodiments, the secondary circuit 30 can include a second bypass 68, a third valve 70, a fourth valve 72, and a fifth valve 74, all of which are illustrated with dotted lines. The second bypass 68 of the secondary circuit 30 extends and conveys the coolant between a node I of the main pathway 54 of the secondary circuit 30 intermediate the flow control device 58 and the fourth heat exchanger 26 to a node J of the main pathway 54 of the secondary circuit 30 intermediate the second heat exchanger 16 and the flow control device 58.

The third valve 70 of the secondary circuit 30 can be disposed in the main pathway 54 of the secondary circuit 30 intermediate the second heat exchanger 16 and the first valve 60 of the secondary circuit 30. The third valve 70 controls the flow of coolant through a portion of the main pathway 54 of the secondary circuit 30. The fourth valve 72 of the secondary circuit 30 can be disposed intermediate node I and the node G of the main pathway 34 of the secondary circuit 30. The fourth valve 72 controls the flow of coolant through a portion of the main pathway 54 of the secondary circuit. The fifth valve 74 of the secondary circuit 30 can be disposed in the second bypass 68 to control the flow of coolant therethrough. It is understood that more or fewer valves can be disposed in the main pathway 54 and the second bypass 68 of the secondary circuit 30, as desired. Additionally, further more or fewer bypasses can be included with the secondary circuit 30, as desired.

In operation, the HVAC system 10 conditions the air flowing from the source of air to the passenger compartment. A direction of the flow of air through the housing 12 is indicated by an arrow. The HVAC system 10 can operate in a cooling mode to cool the passenger compartment, a heating mode to heat the passenger compartment, and a demist mode to dehumidify the passenger compartment.

In FIG. 2, a cooling mode of the HVAC system 10 is illustrated. In the cooling mode, the refrigerant is conveyed through the primary circuit 20 in the first direction. The first direction of the flow of the refrigerant through the primary circuit 20 is indicated by arrowheads. The first valve 42 of the primary circuit 20, the second valve 44 of the primary circuit 20, and the third valve 46 of the primary circuit 20 are in an open position to permit the refrigerant to flow through the main pathway 34 of the primary circuit 20. The fourth valve 48 of the primary circuit 20, the fifth valve 50 of the primary circuit 20, and the sixth valve 52 of the primary circuit 20 are closed to militate against the refrigerant flowing through the bypasses 36, 38, 40 of the primary circuit 20.

With continuing reference to FIG. 2, the refrigerant is compressed in the compressor 22 and then conveyed to the third heat exchanger 24. The third heat exchanger 24 transfers heat from the refrigerant to the air conveyed by the fan 28. The heated air through the third heat exchanger 24 is then conveyed to the atmosphere. The refrigerant is then conveyed through the fourth heat exchanger 26, which is idle in the cooling mode, to the first expansion valve 32, where the refrigerant is expanded. The first heat exchanger 14, configured as an evaporator, receives the flow of refrigerant from the first expansion valve 32. Heat is transferred from the air flowing in the housing 12 to the refrigerant received by the first heat exchanger 14. The air flowing in the housing 12 is cooled and is conveyed to the passenger compartment.

Concurrently, the coolant is conveyed through the secondary circuit 30 to cool the battery 11. A direction of the flow of coolant through the secondary circuit 30 is indicated by arrowheads. The first valve 60 of the secondary circuit 30 is closed to militate against the coolant flowing through a portion of the main pathway 54 of the secondary circuit 30. The second valve 64 of the secondary circuit 30 is open to permit the coolant to flow through the bypass 56 of the secondary circuit 30.

The flow control device 58 causes the coolant to flow through the bypass 56 and a portion of the main pathway 54 of the secondary circuit 30 and, consequently, through the second heat exchanger 16. The air which has been cooled by the first heat exchanger 14 is conveyed through the second heat exchanger 16. A transfer of heat from the coolant to air occurs through the second heat exchanger 16 to cool the coolant flowing through the secondary circuit 30. The coolant is then conveyed from the second heat exchanger 16 to the bypass 56 of the secondary circuit 30 to cool the battery 11. As the coolant is conveyed through the bypass 56, a transfer of heat occurs between the battery 11 and the coolant flowing through the bypass 56 of the secondary circuit 30. During the cooling mode, the second heat exchanger 16 only minimally transfers heat from the coolant to the air to substantially maintain a desired temperature of the 1 air conveyed to the passenger compartment.

In FIG. 3, a demist mode of the HVAC system 10 is illustrated. The refrigerant flowing through the primary circuit 20 during the demist mode is similar to the refrigerant flowing through the primary circuit 20 during the cooling mode as illustrated in FIG. 2 and described hereinabove. The first direction of the flow of the refrigerant through the primary circuit 20 is indicated by arrowheads. Heat is transferred from the air flowing in the housing 12 to the refrigerant received by the first heat exchanger 14. The air flowing in the housing 12 is cooled and dehumidified by the first heat exchanger 14 and conveyed through the second heat exchanger 16.

During the demist mode, the coolant is conveyed through the secondary circuit 30 to reheat the air flowing through the housing 12. The first valve 60 of the secondary circuit 30 is open to permit the coolant to flow through the main pathway 54 of the secondary circuit 30. The second valve 64 of the secondary circuit 30 is closed to militate against the coolant flowing through the first bypass 56 of the secondary circuit 30.

The flow control device 58 causes the coolant to flow through the main pathway 54 of the secondary circuit 30. The coolant is conveyed through the fourth heat exchanger 26. The fourth heat exchanger 26 transfers heat from the refrigerant flowing through the primary circuit 20 to the coolant flowing through the secondary circuit 30 to warm the coolant. The warm coolant is then conveyed to the second heat exchanger 16. Concurrently, the second heat exchanger 16 receives the cooled and dehumidified air from the first heat exchanger 14. The second heat exchanger 16 transfers heat from the coolant to the air to reheat the air flowing through the housing 12 before being conveyed to the passenger compartment.

In certain embodiments, a speed of the fan 28 can be selectively adjusted to control a temperature of the air conveyed through the second heat exchanger 16. For example, the speed of the fan 28 can be decreased to cause the second heat exchanger 16 to increase the amount of heat transferred to the air conveyed through the second heat exchanger 16. Conversely, the speed of the fan 28 can be increased to cause the second heat exchanger 16 to decrease the amount of heat transferred to the air conveyed through the second heat exchanger 16.

In FIG. 4, a heating mode of the HVAC system 10 is illustrated. In the heating mode, the refrigerant is conveyed through the primary circuit 20 in the second direction. The second direction of the flow of the refrigerant through the primary circuit 20 is indicated by arrowheads. The first valve 42 of the primary circuit 20, the second valve 44 of the primary circuit 20, and the third valve 46 of the primary circuit 20 are closed to militate against the refrigerant flowing through portions of the main pathway 34 of the primary circuit 20. The fourth valve 48 of the primary circuit 20, the fifth valve 50 of the primary circuit 20, and the sixth valve 52 of the primary circuit 20 are open to permit the refrigerant to flow through the bypasses 36, 38, 40 of the primary circuit 20.

With continuing reference to FIG. 4, the refrigerant is compressed in the compressor 22 and then conveyed to the first heat exchanger 14, configured as a heater core. The first heat exchanger 14 transfers heat from the refrigerant to the air being conveyed through the housing 12. The air is conveyed through the second heat exchanger 16, which is idle, to the passenger compartment. The refrigerant is then conveyed through the second expansion valve 33, where the refrigerant is expanded. The refrigerant is then conveyed through the fourth heat exchanger 26, which is idle, to the third heat exchanger 24 where heat is transferred from the air conveyed by the fan 28 to the refrigerant. The refrigerant is then conveyed to the compressor 22 to be compressed again by the compressor 22.

During the heating mode, the secondary circuit 30 is idle. However in another embodiment of the disclosure, as illustrated in FIG. 4, where the secondary circuit 30 includes the second bypass 68, the secondary circuit 30 can convey the coolant through the second bypass 68 of the secondary circuit 30 to cool the battery 11. The flow of coolant is indicated by the arrowheads.

According to this embodiment, in the heating mode, the first valve 60 of the secondary circuit 30, the second valve 64 of the secondary circuit 30, and the fifth valve 74 of the secondary circuit 30 are open to permit the coolant to flow through the first bypass 56 of the secondary circuit 30, the second bypass 68 of the secondary circuit 30, and a portion of the main pathway 54 of the secondary circuit 30. The third valve 70 of the secondary circuit 30 and the fourth valve 72 of the secondary circuit 30 are closed to militate against the refrigerant flowing through portions of the main pathway 54 of the secondary circuit 30.

The flow control device 58 causes the coolant to flow through the first bypass 56 of secondary circuit 30. The coolant is then conveyed through the fourth heat exchanger 26. The fourth heat exchanger 26, which is in operation, transfers heat from the coolant through the secondary circuit 30 to the refrigerant flowing through the primary circuit 20 to cool the coolant. The coolant is then conveyed through the second bypass 68 of the secondary circuit 30 back to the flow control device 58. As the coolant is conveyed through the first bypass 56, heat is transferred from the battery 11 to the coolant to cool the battery 11.

FIG. 5 illustrates an HVAC system 10′ according to another embodiment of the invention. Similar reference numerals are used to describe features substantially similar to those described in FIGS. 1-4 except with a prime (′) symbol placed after the reference numerals. The HVAC system 10′ is substantially similar to the HVAC system 10 of FIGS. 1-4 and described hereinabove, except the secondary circuit 30′ is in fluid communication with the primary circuit 20′ and conveys the refrigerant through the second heat exchanger 16′. The second heat exchanger 16′ is configured to transfer heat between the air flowing through the housing 12′ and the refrigerant flowing therethrough. The secondary circuit 30′ in fluid communication with the primary circuit 20′ is employed during the demist mode of the HVAC system 10′ to reheat the air flowing through the housing 12′ instead of the fourth heat exchanger 26 of the HVAC system 10 of FIGS. 1-4.

According to this embodiment, the primary circuit 20′ includes a seventh valve 82 disposed intermediate the third heat exchanger 24′ and node E. The seventh valve 82 controls the refrigerant flowing through a portion of the main pathway 34 of the primary circuit 20′. The secondary circuit 30′ extends and conveys the refrigerant through the second heat exchanger 16′ from a node K of the primary circuit 20′ intermediate the third heat exchanger 24′ and the seventh valve 82 to a node L of the primary circuit 20′ intermediate the seventh valve 82 and node E. The secondary circuit 30′ includes a valve 80 to control the refrigerant flowing therethrough. It is understood that more than one valve can be employed to control the refrigerant flowing through the secondary circuit 30′, as desired.

FIG. 6 illustrates the cooling mode of the HVAC system 10′ according to an embodiment of the disclosure. The cooling mode of the HVAC system 10′ is similar to the cooling mode of the HVAC system 10 of FIG. 2, described hereinabove, except the secondary circuit 30′ and the second heat exchanger 16′ are idle. The seventh valve 82 of the primary circuit 20′ is open to permit the refrigerant to flow through the portion of main pathway 34′ of the primary circuit 20′ between the node K and the node L. The valve 80 of the secondary circuit 30′ is closed to militate against the refrigerant flowing through the secondary circuit 30′.

The flow of the refrigerant through the primary circuit 20′ is indicated by the arrows. The refrigerant is compressed in the compressor 22′ and then conveyed to the third heat exchanger 24′. The third heat exchanger 24 transfers heat from the refrigerant to the air conveyed by the fan 28′. The heated air through the third heat exchanger 24′ is then conveyed to the atmosphere. The refrigerant is then conveyed to the first expansion valve 32′, where the refrigerant is expanded. The first heat exchanger 14′, configured as an evaporator, receives the flow of refrigerant from the first expansion valve 32′. Heat is transferred from the air flowing in the housing 12′ to the refrigerant received by the first heat exchanger 14′. The air flowing in the housing 12′ is cooled and is conveyed to the passenger compartment.

FIG. 7 illustrates the demist mode of the HVAC system 10′ according to an embodiment of the disclosure. The demist mode of the HVAC system 10′ is similar to the demist mode of the HVAC system 10 of FIG. 3, described hereinabove, except the second heat exchanger 16′ receives the flow of refrigerant and transfers heat from the refrigerant to the air flowing through the housing 12′. The seventh valve 82 of the primary circuit 20′ is closed to militate against the refrigerant flowing through the portion of main pathway 34′ of the primary circuit 20′ between the node K and the node L. The valve 80 of the secondary circuit 30′ is open to permit the refrigerant to flow through the secondary circuit 30′. The first heat exchanger 14′ cools the air flowing through the housing 12′ to dehumidify the air and the second heat exchanger 16′ reheats the air before the air is conveyed to the passenger compartment.

The flow of the refrigerant through the primary circuit 20 and through the secondary circuit 30′ is indicated by the arrows. The flow of the refrigerant through the primary circuit 20′ is indicated by the arrows. The refrigerant is compressed in the compressor 22′ and then conveyed to the third heat exchanger 24′. The third heat exchanger 24 transfers heat from the refrigerant to the air conveyed by the fan 28′. The heated air through the third heat exchanger 24′ is then conveyed to the atmosphere. The refrigerant is then conveyed to the second heat exchanger 16′, where heat is transferred from the coolant flowing through the second heat exchanger 16′ to the cooled and dehumidified air flowing through the housing 12′ and then to the first expansion valve 32′, where the refrigerant is expanded. The first heat exchanger 14′, configured as an evaporator, receives the flow of refrigerant from the first expansion valve 32′. Heat is transferred from the air flowing in the housing 12′ to the refrigerant received by the first heat exchanger 14′. The air flowing in the housing 12′ is cooled and is conveyed to the passenger compartment.

In certain embodiments, a speed of the fan 28′ can be selectively adjusted to control a temperature of the air conveyed through the second heat exchanger 16′. For example, the speed of the fan 28′ can be decreased to cause a decrease in a flow rate of the air flowing through the third heat exchanger 24′. The decrease in the flow rate of the air flowing through the third heat exchanger 24′ causes a decrease in an amount of heat transferred from the coolant to the air flowing through the third heat exchanger 24′. Therefore, with decreased fan speed, an amount of heat contained in the coolant flowing from the third heat exchanger 24′ through the secondary circuit 30′ to the second heat exchanger 16′ is greater than an amount of heat contained in the coolant flowing from the third heat exchanger 24′ through the secondary circuit 30′ to the second heat exchanger 16′ with increased fan speed. Thus, the second heat exchanger 16′ receiving the coolant with a greater amount of heat. Therefore, the amount of heat transferred to the air conveyed through the second heat exchanger 16′ is increased. Conversely, the speed of the fan 28′ can be increased to cause the second heat exchanger 16′ to decrease the amount of heat transferred to the air conveyed through the second heat exchanger 16′.

FIG. 8 illustrates the heating mode of the HVAC system 10′ according to an embodiment of the disclosure. The heating mode of the HVAC system 10′ is similar to the heating mode of the HVAC system 10 of FIG. 4, described hereinabove, except the secondary circuit 30′ and the second heat exchanger 16′ are idle. The seventh valve 82 of the primary circuit 20′ is open to permit the refrigerant to flow through the portion of the main pathway 34′ of the primary circuit 20′ between the node K and the node L. The valve 80 of the secondary circuit 30′ is closed to militate against the refrigerant flowing through the secondary circuit 30′.

The flow of the refrigerant through the primary circuit 20′ is indicated by the arrows. The first heat exchanger 14′ heats the air flowing through the housing 12′ to heat the passenger compartment. The refrigerant is compressed in the compressor 22 and then conveyed to the first heat exchanger 14, configured as a heater core. The first heat exchanger 14 transfers heat from the refrigerant to the air being conveyed through the housing 12. The air is conveyed through the second heat exchanger 16, which is idle, to the passenger compartment. The refrigerant is then conveyed through the second expansion valve 33, where the refrigerant is expanded. The refrigerant is then conveyed to the third heat exchanger 24 where heat is transferred from the air conveyed by the fan 28 to the refrigerant. The refrigerant is then conveyed to the compressor 22 to be compressed again by the compressor 22. The first heat exchanger 14′ transfers heat from the refrigerant flowing therethrough to the air flowing through the housing 12 to heat the air flowing through the housing 12′ and heat the passenger compartment.

Advantageously, the HVAC system 10, 10′ efficiently heats, cools, and dehumidifies the air flowing to the passenger compartment by utilizing waste heat from the refrigeration system. The primary circuit 20, 20′ is configured for both a refrigeration plant operation and a heat pump operation and integrates the secondary circuit 30, 30′ in fluid communication with the second heat exchanger 16, 16′ to maintain cost, weight, and package size requirements. The second heat exchanger 16, 16′ militates against a need for an HVAC system with blend doors, which minimizes complexity, vibrations, noise, and occupied vehicle space. Additionally, in certain embodiments, the HVAC system 10 can cool the battery 11 of the electric vehicle to maintain performance efficiency of the battery 11.

From the foregoing description, one ordinarily skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications to the invention to adapt it to various usages and conditions. 

What is claimed is:
 1. An HVAC system of an electric vehicle comprising: a housing having an inlet for receiving a flow of air therethrough and an outlet in fluid communication with a passenger compartment of the vehicle; a first heat exchanger disposed in the housing and configured to receive the flow of air therethrough; a second heat exchanger disposed in the housing downstream from the first heat exchanger with respect of a direction of the flow of air through the housing, the second heat exchanger configured to receive the flow of air; a primary circuit containing a refrigerant therein and in fluid communication with the first heat exchanger, the primary circuit including a compressor, a third heat exchanger, at least one expansion valve, and a plurality of valves, each of the valves cooperating with each other to selectively convey the refrigerant through the first heat exchanger in a first direction and a second direction; and a secondary circuit in one of fluid communication with and heat exchange communication with a portion of the primary circuit intermediate the third heat exchanger and the at least one expansion valve, the secondary circuit in fluid communication with the second heat exchanger.
 2. The HVAC system of claim 1, wherein the second heat exchanger is separate from the first heat exchanger.
 3. The HVAC system of claim 1, wherein the second heat exchanger is one of integrally formed with the first heat exchanger, coupled to the first heat exchanger, and abutting with the first heat exchanger.
 4. The HVAC system of claim 1, wherein the second heat exchanger has a width less than a width of the first heat exchanger.
 5. The HVAC system of claim 1, wherein the first heat exchanger is configured to be an evaporator to receive the refrigerant conveyed therethrough in the first direction and a heater core to receive the refrigerant conveyed therethrough in the second direction.
 6. The HVAC system of claim 1, wherein the primary circuit includes at least one bypass cooperating with the plurality of valves to convey the refrigerant through the first heat exchanger in the second direction.
 7. The HVAC system of claim 1, wherein the primary circuit includes a fourth heat exchanger disposed adjacent and in fluid communication with the third heat exchanger.
 8. The HVAC system of claim 7, wherein the secondary circuit is in heat exchange communication with the primary circuit and in fluid communication with the fourth heat exchanger.
 9. The HVAC system of claim 1, wherein the secondary circuit contains one of the refrigerant and a coolant.
 10. The HVAC system of claim 9, wherein the secondary circuit includes at least one of a valve and a bypass to selectively control a direction of a flow of the one of the refrigerant and the coolant.
 11. The HVAC system of claim 1, wherein the secondary circuit is in heat exchange communication with the primary circuit and contains a coolant and a fluid control device for conveying the coolant therethrough.
 12. The HVAC system of claim 1, wherein the secondary circuit is in heat exchange communication with a battery of the vehicle.
 13. A method for operating an HVAC system of an electric vehicle comprising the steps of: providing a housing having an inlet for receiving a flow of air therethrough and an outlet in fluid communication with a passenger compartment of the vehicle; disposing a first heat exchanger in the housing and a second heat exchanger in the housing downstream from the first heat exchanger with respect of a direction of the flow of air; providing a primary circuit containing a refrigerant therein and configured to operate in at least a cooling mode, a demist mode, and a heating mode, the primary circuit having a compressor, a third heat exchanger, and at least one expansion valve each in fluid communication with the first heat exchanger; directing the refrigerant to flow through the first heat exchanger in a first direction during the cooling mode and the demist mode and in a second direction during the heating mode; and providing a secondary circuit in fluid communication with the second heat exchanger and in one of fluid communication with and heat exchange communication with a portion of the primary circuit intermediate the third heat exchanger and the at least one expansion valve.
 14. The method of claim 13, further comprising the steps of directing one of the refrigerant and a coolant to flow through the second heat exchanger during the demist mode.
 15. The method of claim 13, wherein the primary circuit includes a plurality of valves and a plurality of bypasses cooperating with each other to direct the refrigerant through the first heat exchanger in first direction and the second direction.
 16. The method of claim 13, wherein the secondary circuit is in heat exchange communication with the primary circuit, the primary circuit includes a fourth heat exchanger providing the heat exchange communication between the primary circuit and the secondary circuit, the fourth heat exchanger in fluid communication with and adjacent to the third heat exchanger.
 17. The method of claim 13, wherein the secondary circuit is in heat exchange communication with the primary circuit and contains a coolant therein, the secondary circuit includes at least one valve and at least one bypass cooperating with each other to direct the coolant to flow through the secondary circuit.
 18. The method of claim 17, further comprising the steps of: disposing the at least one bypass in heat exchange communication with a battery of the electric vehicle; and directing the coolant to flow through the bypass of the secondary circuit to transfer heat from the battery to the coolant during at least one of the cooling mode and the heating mode.
 19. The method of claim 14, further comprising the steps of: providing a fan adjacent the third heat exchanger to convey air through the third heat exchanger; and adjusting a speed of the fan to control an amount of heat transferred to the air conveyed through the housing by the second heat exchanger.
 20. A method for operating an HVAC system of an electric vehicle comprising the steps of: providing a housing having an inlet for receiving a flow of air therethrough and an outlet in fluid communication with a passenger compartment of the vehicle; disposing a first heat exchanger in the housing and a second heat exchanger in the housing downstream from the first heat exchanger with respect of a direction of the flow of air; providing a primary circuit containing a refrigerant therein and configured to operate in at least a cooling mode, a demist mode, and a heating mode, the primary circuit having a compressor, a third heat exchanger, and at least one expansion valve each in fluid communication with the first heat exchanger; directing the refrigerant to flow through the first heat exchanger in a first direction during the cooling mode and the demist mode and in a second direction during the heating mode; providing a secondary circuit in fluid communication with the second heat exchanger and in one of fluid communication with and heat exchange communication with a portion of the primary circuit intermediate the third heat exchanger and the at least one expansion valve; and directing one of the refrigerant and a coolant to flow through the second heat exchanger during the demist mode. 